Improved mode of preparing ores



I UNITED STATES PATENT OEEICE.

EDWARD N. KENT, OF NEWV YORK, N. Y.

IMPROVED MODE OF PREPARING ORES.

Specification forming part of Letters Patent No. 15,048, dated November15, 1864.

To all whom it may concern Be it known that I, EDWARD N. KENT, of theUnited States Assay Office, in the city, county, and StateofNewYork,haveinvented a new and useful Improvement in the Preparationof Ores; and I do hereby declare that the following is a full, clear,and exact description thereof, which will enable those skilledin the artto fully understand and use the same.

My invention consists in taking tailings or crushed ore as it comes fromthe stamps or mills and mixing it with a solution of chloride of sodiumor its equivalent in such proportions as to form a stiff paste,and thenform or press it into cakes, lumps, or hiicks, which, after drying byexposure to the air, are calcined in a common stove, furnace, heap,orkiln'constructed so as to have a draltof heated air through theinterstices of the cakes, lumps,or bricks in such a manner as to bringthechemical into the most intimate contact with every particle of thecrushed ore, and admit of the subsequent calcination in the best andcheapest manner.

I am aware that dry salt has been used for calcination in areverberatory furnace; butin this case a great deal of manual labor isrequired at the furnace, and by constant stirring a large amount of dustis lost. The salt and ore cannot be so intimately mixed, the chemicalaction is less perfect, and the quantity of ore operated upon is limitedto the capacity of the furnace, which is very expensive.

I am also aware that water has been used for making a paste of certainores with lime or clay for smelting; but I am not'aware that salt andwater together, or a solution of salt, has been before used for thepurposes herein specified.

By the use of a solution of salt and by caking the ore a common stove,furnace, or kiln, such as is usedfor burning lime or bricks, may be usedfor the calcination of crushed ores or tailings; or the caked ore may becalcined in heaps. No manual labor or stirringis required during thecalcination, and consequently no dust. is lost. The mixture of the saltand ore is perfect,and the quantity operatedupon may be almostunlimited, as in a limekiln the pro cess ofcalcination is continuous,and a brickkiln of ordinary dimensions containing five hundred thousandbricks of five pounds each would equal one thousand two hundred andfifty tons of ore to be calcined at one operation. It is estimated thatone cord of wood is sufficient fuel for two thousand bricks or five tonsof ore, and that ten thousand bricks or twenty-five tons of ore can beprepared with one machine per day.

Ore prepared in this manner is not only desulphurized in the best mannerwithout the trouble and expense of building reverberatory furnaces, andthe loss of dust by constantstirring or violent agitation in a currentof air, but it contains all the metals, except gold, in the condition ofchlorides, and when these are dissolved or decomposed the gold, if anyis present,is left clear and bright and in the best possible conditionfor amalgamation.

Arsenic, zinc, and antimony are the most troublesome metals in oressubmitted to amalgamation; but by this process of preparingthe ore thesemetals are removed as volatile and soluble chlorides during thecalciuation and subsequent amalgamation, and when the last operation isperformed in close vessels, or by the barrel process,with metallic ironand m'ercury the chloride of silver is reduced to metallic silver andsaved, and more gold may thus be obtained than by any other processot'amalgamation; but by any process of amalgamation more gold can beobtained from the prepared ore than from crude ore or roasted ore whencalcined or roasted alone.

By washing pyritic ores prepared by this process an acid solution ofnickel, copper,zinc, or iron, according to the nature of the ore,together With sulphate of soda and other salts, is obtained, from whichthe metals may be precipitated by soda, lime, iibmsulphureted hydrogenor sulphide of sodium; or the solution may be evaporated at once todryness, and from the chlorides thus obtained the metals, or any othercompound of the metals, may be prepared without difficulty and with lessexpense than by the use of acids.

Al'teramalgamaringor washing theprepared ore the failings may beconcentrated to oneor two per cent. of its former weight, and, if dosirable, this may be smelted for nickel matte, or metallic lead, ifthese metals are present; but I prefer to dress or concentrate thetailings in such a manner as to leave about onefourth (more or less) ofthe original weight of the ore, and, after draining the concentratedresidue or dressed ore, to mix this with sufficient crude ore andsolution of salt to make the original quantity, and calcine, wash, oramalgamate as before, and so on continuously.

In this way the valuable metals and the im-,

purities in the native ores are gradually separated, and theconcentrated residue becoming constantly richer at every subsequentconcentration, the quantity of gold which may be obtained by closeamalgamation from ores prepared by this process averages fromseventyfive per cent. to the full assay value of the ore.-

Having thus described my invention, I claim asnew and desire to secureby Letters Patent 1. The preparation of crushed or pulverized ores andtailings by caking them with a solution of chloride of sodium, or saltand water, introduced in any manner, so as to admit of forming thecrushed ore into cakes, lumps, or bricks, as specified.

2. The calcination of crushed ores and tailings in a common stove,furnace, heap,orkiln when previously prepared by the use of a solutionof chloride of sodium, or salt and water, and made into lumps of anyform, so as to admit of thedecomposition of the salt by the passage of acurrent of heated air through the interstices of the lumps so formed,substantially as herein described.

EDWARD N. KENT. Witnesses:

M. M. LIVINGSTON, I. P. HALL.

